These images earned Bartletti a Pulitzer Prize in feature photography in 2003. That six-part photo essay was about Honduran youths, some as young as 12, clinging to freight trains bounding north through Mexico toward the U.S. border. The Pulitzer jury commended Bartletti for his "memorable portrayal of how undocumented Central American youths, often facing deadly danger, travel north to the United States." The work was also honored with the Robert F. Kennedy Prize for photojournalism and the George Polk Award.

"For three months I clung to the top, the side and the belly of 'The Beast' as it carried its vulnerable cargo of men and boys closer and closer to the U.S.-Mexico border. The end station came only to the brave and the lucky."

Clinging to the end of a speeding boxcar, Santo Antonio Gamay, 25, shows the fatigue of 15 hours riding a freight train. He's minutes from leaping off, in an attempt to outrun Mexican immigration authorities at the Tonala, Chiapas, checkpoint. The Honduran had been arrested three times there and deported to the Guatemala border. He was trying to get to Toronto. (Don Bartletti / Los Angeles Times)

In the vast migration that is changing the U.S., a Honduran boy rides a freight train through Mexico. Each year thousands of undocumented Central Americans stow away for 1,500 miles on the tops and sides of trains. Some are parents desperate to escape poverty. Many are children in search of a parent who left them behind long ago. (Don Bartletti / Los Angeles Times)

In the Chiapas, Mexico, countryside, a boy and girl race their horse alongside a freight train. The fleeting scene brought a few moments of joy to young Honduran stowaways who have learned to fear the worst from people along the rails. (Don Bartletti / Los Angeles Times)

Mexicans pass food to Central American migrants aboard a train as it passes through Fortin de las Flores, Mexico. The generosity of the poor residents along the tracks through Veracruz state is well-known among train-riding stowaways. (Don Bartletti / Los Angeles Times)

Clinging to the top of a speeding freight train, migrants duck under dangerously close tree branches. Honduran stowaways call the migration route through Mexico "the Beast" for its life-threatening hazards. (Don Bartletti / Los Angeles Times)

La Mesa Penitentiary, Tijuana

"The prison was very scary, very corrupt. While I was there, there were three deaths."

A trio of inmates at the infamous La Mesa Penitentiary in Tijuana in 1999 show off tattoos and scars. In 2002, the sprawling village that prisoners had built in its courtyard was bulldozed. (Don Bartletti / Los Angeles Times)

"When the cartel violence first blew up in Tijuana, I spent a week with photojournalists there who could help me find the hot spots without getting killed."

Relatives of one of five slain state and federal policemen weep near the officers' truck, which was ambushed by gunmen in Culiacan in November 2008. More than 4,000 people had already died that year in Mexico's drug war. (Don Bartletti / Los Angeles Times)

With weapons still at their sides, the bodies of two plainclothes state policemen lie in the bed of a pickup in November 2008. They and three federal policemen were assassinated in a hail of automatic gunfire as they drove through the middle of Culiacan. (Don Bartletti / Los Angeles Times)

"This little boy was looking down on his dead brother, who had sold marijuana on the street."

Arturo, 9, stares at the body of his brother Felipe Alejandro Prado, 19, who was killed during a drive-by shooting in a tough hillside slum in southeastern Tijuana in 2008. (Don Bartletti / Los Angeles Times)

"A combination of plastic, marijuana and prescription drugs, and syringes."

Officials burn confiscated drugs, including more than two tons of marijuana, cocaine, heroin and prescription pills, during a ceremony at an army base outside Tijuana in February 2009. (Don Bartletti / Los Angeles Times)

"The drug lords bury their families there. There are double-pane windows and air conditioning and little patios where they party at the mausoleums."

In November 2008, relatives embrace at a Culiacan cemetery favored by drug dealers. Some of the crypts are built with imported Italian marble, mosaics, crystal chandeliers, Corinthian columns and French doors. (Don Bartletti / Los Angeles Times)

"I once hired a fixer to alert me to dangers, but he said: 'I don't want you to walk next to me; walk in front of me.' Because he was so afraid the cartel would finger him."

Mexican federal police drive through Matamoros in July 2012. The local police force disbanded, and government troops had limited control of roads in a region where criminal gangs had seized control of major streets and highways. (Don Bartletti / Los Angeles Times)

U.S.-Mexico Border

"Without the flashlight it was the darkest place you could imagine."

Searching for smugglers a mile inside a drainage tunnel, U.S. Border Patrol Agent Jim Amstedz pulls open a steel gate that defines the U.S.-Mexico border. Agents Scott Connors, left, and Scott Wencel hold weapons at the ready. Smugglers run drugs and people through the gate and into the U.S. (Don Bartletti / Los Angeles Times)

"I'm always interested in the evolution of the border. Activity along the fence line is high drama that defines a part of our relationship with Mexico. It’s like theater, with no intermission."

A U.S. Border Patrol agent rides along the fence at Imperial Sand Dunes in California's southeast corner in March 2009. The patrol came during a period of steep decline in migrants crossing illegally. (Don Bartletti / Los Angeles Times)

"This was an amazing two weeks, with Border Patrol trackers trying to catch these marijuana smugglers."

"This is one of the most lethal corridors in Texas, where the desert and the hot sand swallow up people trying to walk around a checkpoint."

Alonzo Rangel takes notes at the scene of the death of a migrant woman in south Texas in April 2013. At that point, 31 bodies had been found that year in the heavily trafficked migrant smuggling corridor. (Don Bartletti / Los Angeles Times)

"We were in a border town where institutionalized smuggling was the only industry. I counted, at one point, 120 people walking in single file through the southern Arizona desert."

Migrants hurry through a desolate landscape of leafless trees and cactus near Sasabe, Mexico, in February 2007. Because of increased security along the U.S.-Mexico border, most were likely to be caught or to quit the journey. (Don Bartletti / Los Angeles Times)

"I was covering the wildfire on the border east of San Diego. The fire consumed all the vegetation, revealing a network of migrant trails. Firemen were bringing victims to the UC San Diego burn center by the truckloads."

Concepcion Peralta prays before a memorial he set up next to Highway 94, near the site where his daughter Areli, her husband, Ruben, and their friend Lourdes had died. All three were killed in the 2007 Harris fire while trying to make their way into the U.S. (Don Bartletti / Los Angeles Times)

Relatives of Ruben Santos Ramirez weep at his coffin. He was among seven migrants killed in the 2007 Harris fire while trying to cross into the U.S. (Don Bartletti / Los Angeles Times)

"He spent 10 days walking in the desert with his girlfriend. It almost killed him, but he made it back."

In October 2011, Luis Luna, 19, considers crossing back into the U.S. via the undercarriage of a freight car. Earlier that year, Luna, who was raised in the U.S., was ordered back to Mexico after he was pulled over for having a broken headlight. (Don Bartletti / Los Angeles Times)

Honduran Alejandro Maldonado, 47, who was deported after working four years at an apple orchard in Alexandria, Va., beds down in a graveyard in Nogales, Mexico, in 2011. Luis Luna, who was also there, said: "I can't sleep here -- I'm scared a dead person will grab my feet." (Don Bartletti / Los Angeles Times)

Bartletti shot this photo at Campo Sacramento, in the Mexican state of Sinaloa, while reporting on conditions on Mexican farms. He’d been invited into the camp by a family who shared their bare, 12-by-12-foot room with him. When he left the temporary home, a guard saw him, approached and told him to leave the camp.

"That was the moment I spotted a little boy playing with a kite made out of a plastic bag. I thought, how interesting. Here is something absolutely beautiful among these chicken coops of humanity."

Behind the high fence that surrounds Campo Sacramento in Guasave, Sinaloa, 7-year-old Udiel Castro plays with a kite he fashioned from a plastic grocery bag. Udiel's family, like many migrant farmworkers in Mexico, are indigenous people from some of the poorest parts of the country. (Don Bartletti / Los Angeles Times)